feat(verify): ABI checks on arm64, riscv64 and loong64

Assisted-by: GLM 5.3 Flash

verify/abi.go

@@ -0,0 +1,71 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build amd64 || arm64 || riscv64 || loong64
+
+package verify
+
+import (
+	"encoding/binary"
+	"fmt"
+	"syscall"
+	"unsafe"
+)
+
+// CallChecked invokes the function at fnAddr with ABI sentinels and a
+// canary below SP, returning both the argument block (with results) and an
+// ABIReport.
+//
+// The architecture-specific parts live in abi_<arch>.s: enterJITChecked
+// plants sentinels in the registers the Go ABI fixes across calls (the
+// frame pointer and the goroutine pointer) before switching to the
+// prepared stack, and the raw return trampoline leaveJITCheckedRaw
+// compares them and records violations in abiResult.
+func CallChecked(fnAddr uintptr, args []byte) ([]byte, ABIReport, error) {
+	report := ABIReport{}
+
+	// Reset the global result.
+	abiResult = 0
+
+	// Prepare the stack: [canary][padding][leaveJITCheckedRaw][args...]
+	// The canary sits below the initial SP, so the function would have to
+	// write below SP to corrupt it.
+	totalSize := redZoneSize + stackPad + 8 + len(args) + 64
+	stackMem, err := syscall.Mmap(-1, 0, totalSize,
+		syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_PRIVATE|syscall.MAP_ANON)
+	if err != nil {
+		return nil, report, fmt.Errorf("verify: stack mmap: %w", err)
+	}
+	defer func() { _ = syscall.Munmap(stackMem) }()
+
+	// Fill the canary window with the detection pattern.
+	for i := range redZoneSize {
+		stackMem[i] = redZoneFill
+	}
+
+	// Return address and args after the canary and padding.
+	retOff := redZoneSize + stackPad
+	binary.LittleEndian.PutUint64(stackMem[retOff:retOff+8], uint64(leaveCheckedPtr))
+	copy(stackMem[retOff+8:], args)
+
+	stackBase := uintptr(unsafe.Pointer(&stackMem[retOff]))
+	enterJITChecked(fnAddr, stackBase)
+
+	// Read the register-clobber result.
+	res := abiResult
+	report.FPClobbered = res&1 != 0
+	report.GClobbered = res&2 != 0
+
+	// Check the canary window.
+	for i := range redZoneSize {
+		if stackMem[i] != redZoneFill {
+			report.RedZoneHit = true
+			break
+		}
+	}
+
+	// Copy out the argument area.
+	out := make([]byte, len(args))
+	copy(out, stackMem[retOff+8:retOff+8+len(args)])
+	return out, report, nil
+}